1. Field of the Invention
The present invention relates to a mold employed in a composite article molding apparatus for molding a composite article, such as a fiber-reinforced plastic article, by a resin transfer molding method (RTM method) which places a woven fabric in a mold, injects a resin into the mold, and heats the resin for hardening.
2. Description of the Related Art
Various composite articles have become used in all industries including the aircraft industry and the automobile industry in recent years and demand for composite articles is progressively increasing. On the other hand, high manufacturing costs of composite articles are a serious problem obstructing the widespread use of composite articles. Active research and development activities have been made for the reduction of the manufacturing costs of composite articles, and a RTM method has come into wide use in recent years.
A composite article molding method disclosed in JP-B No. 5-14834 bends a prepreg sheet formed by impregnating a woven fabrics with a resin to produce a composite article. FIG. 7 shows a mold employed in a known composite article molding apparatus which bends a flat woven fabrics to produce a composite article by the RTM method. As shown in FIG. 7, the mold consists of a lower half mold 80 and an upper half mold 100. The lower half mold 80 is formed by placing a core 82 on a base 81. A woven fabrics 90 not impregnated with a resin is placed on the core 82, and the upper half mold 100 is joined to the lower half mold 80 to bend the woven fabrics 90 in the shape of a channel. Then, a resin is injected into the mold, and the resin is heated for hardening to obtain a composite article, namely, a fiber-reinforced plastic article.
In producing the composite article by bending the woven fabrics 90 impregnated with the resin by the RTM method using the known mold shown in FIG. 7, when the upper half mold 100 is joined to the lower half mold 80, the upper half mold 100 bends the woven fabrics 90 so as to follow the shape of the core 82 , and compresses the woven fabrics 90 so that the original thickness T(1) of the woven fabrics 90 is reduced to a predetermined thickness T(2). As shown in FIG. 8, flange parts 91 of the woven fabrics 90 are compressed between the upper half mold 100 and the core 82 before the upper wall 101 of the upper half mold 100 comes into contact with a web part 92 of the woven fabrics 90. Therefore the woven fabrics 90 is unable to slide along the side surfaces of the core 82 when the upper half mold 100 is further lowered to compress the web part 92 of the woven fabrics 90 so that its thickness T(1) is reduced to the thickness T(2). Consequently, the web part 92 is creased, the strength of the composite article is reduced or the web part 92 cannot be formed in the predetermined thickness T(2).